Method for controlling cooling of ingots in continuous casting apparatus



Jan. 23, 1968 KINJU MACHIDA 3,364,977 METHOD FOR CONTROLLING COOLING OF INGOTS I CONTINUOUS CASTING APPARATUS Filed March 10, 1965 "IIII'HIE PI'OKv mniu hchidd,

ATTORNEY United States Patent 3,364,977 METHOD FOR CONTROLLING COOLING 0F INGOTS IN CONTINUOUS CASTING APPARATUS Kinju Machida, Hitachi-ski, Japan, assignor to Hitachi, Ltd., Tokyo, Japan Filed Mar. 10, 1965, Ser. No. 438,474 Claims priority, application Japan, Mar. 11, 1964, 39/ 13,344 3 Claims. (Cl. 164-89) The present invention relates to an improved method for cooling ingots in continuous casting apparatus.

In continuous casting apparatus, regulation of an amount of sprayed water onto an ingot for the cooling thereof generally has a great influence on various properties at the inside and outside surface of the ingot. For example, cracks may develop internally as well as externally of an ingot if the amount of sprayed water is more than a value which is appropriate for alloy steel or high carbon steel. If the amount of cooling water is too small compared with the appropriate value, solidification of an ingot can not sufficiently take place, which not only results in the formation of internal cracks when the ingot is withdrawn by pinch rolls, but also results in serious trouble caused by the outflow of molten material from the interior of the ingot when the ingot is severed, as by cutting. In the art of continuous casting heretofore employed, therefore, the operation has been carried out in a manner that the ingot is drawn at a constant rate and the amount of sprayed water thereonto is determined with relation to the ingot withdrawal rate. However, an ingot of small cross section necessarily tends to be drawn at a faster rate than is desired and it becomes dilficult to control the amount of steel melt flow from a tundish into an ingot mold so as to maintain a constant steel melt level in the ingot mold. As a means to prevent such difficulty, it has been proposed to control the amount of steel melt flow from a ladle into the tundish. However, such manner of control of the steel melt level results in considerable ditliculty in respect of a satisfactory casting operation. In order therefore to continue stable operation, the ingot withdrawal rate must be controlled, that is, suitably increased and decreased so that the steel melt level in the ingot mold can be maintained constant irrespective of any variation in the amount of steel melt flow from the tundish. For that reason, the casting operation hitherto employed has been effected in a manner that the amount of sprayed water is maintained invariable while the ingot withdrawal rate is varied as required, admitting the abovedescribed drawback involved in this kind of operation. Thus it has been a matter of impossibility to attain proper cooling, and the absence of proper cooling has resulted in ingots of poor quality. Further, in this kind of casting operation, the ingot withdrawal rate becomes generally slower than a predetermined rate for a short period of the order of several minutes at the beginning and at the end of the casting operation and thus the cooling water tends to be sprayed in an excessive amount. This also has been a cause of poor quality of products.

It is therefore the primary object of the present invention to provide an improved method of ingot cooling in which the amount of sprayed water is controlled either electrically or mechanically in response to any variation in the ingot withdrawal rate to thereby obtain products with improved quality.

Other objects and particularities of the present invention will become apparent from the following descrip tion with reference to the accompanying drawings, in which:

FIG. 1 is a schematic front view of a continuous casting apparatus to which the method embodying the present invention is applied; and

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FIG. 2 is a piping diagram of a water spray cooling system in accordance with the present invention.

Referring to FIG. 1 at first, a ladle is illustrated as at 1 which receives a steel melt from a furnace (not shown). The steel melt is poured from the ladle 1 into a tundish 2 which has a nozzle at its bottom through which the steel melt is poured into an ingot mold 3. Reference numeral 4 designates a plurality of apron rollers for guiding the downward movement of an ingot 9; 5, a plurality of spray nozzles for forcing cooling water onto the ingot; and 6 pinch rolls driven from an electric motor 8 through a reduction gearing 7 to cause the downward movement of the ingot 9.

A batch of steel melt is transferred into the ladle 1 from the furnace and the ladle 1 is carried to the continuous casting apparatus. The steel melt is then slowly poured into the tundish 2 and is stored therein for a certain time. Then a predetermined amount of the steel melt is made to flow in a static stream through the nozzle at the bottom of the tundish 2 into the ingot mold 3; meanwhile the ingot mold 3 is water-cooled to cause solidification of the surface portion of the ingot 9 in a short period. The ingot 9 is, at the same time, drawn downwardly by the pinch rolls 6 at a constant rate which balances with the amount of melt being poured into the ingot mold 3. In this operation, the pinch rolls 6 are driven by the electric motor 8 and speed regulation of the pinch rolls 6 is effected by the control of the number of revolutions of the electric motor 8. A vibrator (not shown) is operatively associated with the ingot mold 3 to impart vibration thereto in order that the ingot 9 may not be fractured during the drawing of the ingot 9 by the pinch rolls 6. The ingot 9 being continuously drawn is guided by the apron rollers 4 and, at the same time, cooling water from the water spraying nozzles 5 is directly sprayed onto the surface of the ingot 9 to solidify it deep into its interior. The completely solidified ingot 9 is then severed, as by cutting and carried to other stations.

FIG. 2 shows the arrangement of the spray cooling water supply piping. In FIG. 2, the piping for supply of cooling water is generally indicated at 10 and a pump 11 is disposed therein to effect suction of cooling water from a cooling water reservoir 14 and force the cooling water towards the spray nozzles 5. The pump 11 is driven by an electric motor 12 and a valve 13 is disposed in the piping 10 to regulate the flow of cooling water through the piping 10. A control device 15 is interposed between the electric motors 8 and 12 to control the electric motor 12 so that the latter motor 12 is driven in synchronous relation with the former motor 8.

According to the present invention, the arrangement is such that the amount of sprayed water is regulated in accordance with any variation in the ingot withdrawal rate. In one form of the invention as shown in FIG. 2, the pinch rolls driving motor 8 is associated with the cooling water pump driving motor 12 with the control device 15 interposed therebetween. In this arrangement, the control device 15 detects the number of revolutions of the pinch rolls driving motor 8 and electrically controls the pump driving motor 12 to increase or decrease the number of revolutions thereof as required so that the amount of sprayed water can automatically be regulated in accordance with variation in the withdrawal rate by the pinch rolls 6. In another form of the invention, the cooling water regulating valve 13 may be controlled in accordance with any variation in the number of revolutions of the draw roll driving motor 8. In still another form of the invention, the electric motors 8 and 12 and the regulating valve 13 may be interengaged with each other in a manner that rough regulation can be effected by a combination of the electric motors 8 and 12 and 3 fine regulation can be effected by a combination of the regulating valve 13 and one of the electric motors 8 and 12. The interengaged operation of the electric motors 8 and 12, or of the electric motor 8 and the regulating valve 13 may easily be efiected by any means well known in the art, for example, by a device incorporating therein an electrical computer.

What is claimed is:

1. A method for cooling ingots in a continuous casting apparatus in which the ingot obtained by casting is continuously Withrawn by means of rolls while being cooled by a spray of cooling water, said method comprising continuously adjusting the withdrawal rate of said rolls in accordance with the flow rate of molten metal supplied from a tundish, detecting any variation in the withdrawal rate of said ingot and increasing and decreasing the amount of water sprayed to correspond with the detected variation'in the ingot withdrawal rate.

2. A method according to claim 1, in which said detection is effected by electrical means and said increase and decrease in the amount of sprayed water is also effected by electrical means.

3. A method according to claim 1, in which said detection is efiected by electrical means and said increase and decrease in the amount of sprayed water is effected by mechanical means.

References Cited UNITED STATES PATENTS 2,246,907 6/1941 Webster 164155 2,641,034 6/1953 Harter '16415O 2,682,691 7/1954 Harter 16466 3,237,251 3/1966 Thalrnann 164-4 3,300,820 1/1967 Tiskus et a1. 1 64155 2,206,930 7/1940 Webster 164'155 2,726,430 12/1955 Rossi et a1. 1644 3,176,355 4/1965 SPENCER OVERHOLSER, Primary Examiner.

20 R. S. ANNEAR, Assistant Examiner.

Ljungstromer -164283 

1. A METHOD FOR COOLING INGOTS IN A CONTINUOUS CASTING APPARATUS IN WHICH THE INGOT OBTAINED BY CASTING IS CONTINUOUSLY WITHDRAWN BY MEANS OF ROLLS WHILE BEING COOLED BY A SPRAY OF COOLING WATER, SAID METHOD COMPRISING CONTINUOUSLY ADJUSTING THE WITHDRAWAL RATE OF SAID ROLLS IN ACCORDANCE WITH THE FLOW RATE OF MOLTEN METAL SUPPLIED FROM A TUNDISH, DETECTING ANY VARIATION IN THE WITHDRAWAL RATE OF SAID INGOT AND INCREASING AND DECREASING THE AMOUNT OF WATER SPRAYED TO CORRESPOND WITH THE DETECTED VARIATION IN THE INGOT WITHDRAWAL RATE. 